A sealed integrated circuit typically comprises a ceramic package containing a cavity. The package contains leads extending from the package externally for connection with printed circuit boards or other IC packages. The die containing the electrical circuit is made with bond pads. The die is placed in the ceramic package cavity and the bond die pads are connected to the bond pads in the ceramic package, which in turn are connected to the external leads. The ceramic package is then sealed with a lid placed over the ceramic package, and the die in the cavity. The seal typically may be glass.
In the production of these completed integrated circuits, it is important none of the glass sealant enter into the cavity. The completely packaged integrated circuit may be tested by removing the lid to inspect the cavity for contaminants such as from the glass seal. However, as will be recognized by those skilled in the art, this would be destructive of the IC which would have to be resealed or discarded.
A point source of x-rays has been used to radiate the seal in the ceramic package and produce an image on a plate, Inspection of the plate then would reveal whether any contaminants were allowed to enter the cavity resulting in rejection of the IC.
However, in the prior art, testing of a number of IC packages was prevented by the length formed by line of such tested ICs and the angles formed by the x-ray radiation from the point source on the ICs at the extreme ends of that line. In order to produce a plate by x-ray radiation, which accurately would disclose contaminants in the cavity, it was necessary the x-ray energy source be substantially perpendicular to the IC. This is critical when the IC is placed on an edge and the x-ray radiation is directed to pass through the cavity from side to side to an x-ray sensitive plate. It is important for the x-ray radiation to be substantially perpendicular to the IC so the radiation is directed through the cavity to a plate which records any contaminants in the cavity.
Where the x-ray radiation is not perpendicular to the IC cavity, distortion is produced and the measurement is ineffective.